Cable termination

ABSTRACT

The present invention aims to obtain a simplified connection system for high voltage power cables having ratings up to 400 KV and above. There is obtained a common cable connection system for all accessories and interconnection. The connection system uses a generally applicable interface (4, 5, 6; 13, 14, 15; 30, 40) for interconnection with a number of different apparatus and includes a cable termination (30) consisting of an elastomeric body (36), integrated therein a stress relief device (34), a connector shield (35), an insulation having a conical interface surface (37) and an outer conductive screen (39) and a rigid insulator (41) having a conical interface surface (42) corresponding to the interface surface (37) of the cable termination (30).

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a device for interconnecting a highvoltage cable with an apparatus and/or with a second high voltage cableconsisting of a cable termination and a rigid insulator.

2. Description of the Prior Art

When connecting such high voltage power cables in normal joints, intransition joints, to transformers and other SF6 and oil filledapparatus and accessories and out-door terminals, the interfaces areusually different for each application.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide asimplified connection system for the above cables having ratings up to400 KV and above. The features of the invention are defined in theaccompanying patent claims.

With the present invention there is obtained a common cable connectionsystem for all accessories and interconnections. The interface betweenthe cable end and any accessory, between two cable ends or between twoapparatus is generally applicable, resulting in a number of advantages,such as factory pretesting, reduction of installation time and cost,reduction of tools and simplified field testing.

The stress cone design and dimensions would also be the same for allapplications, the only variation being the diameter of the cable orapparatus entrance.

A further advantage is that the interface components does not includeany gas or oil and, therefore, they cannot leak or explode.

Above mentioned and other features and objects of the present inventionwill clearly appear from the following detailed description ofembodiments of the invention taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 3 illustrate three different principles of interface betweena cable end and accessories,

FIGS. 4 to 12 illustrate several applications of the invention, and

FIG. 13 illustrates a rigid insulator corresponding to the insulatorshown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1, 2 and 3, there are illustrated three interfacemethods,--respectively called an inner cone concept, an outer coneconcept and a no cone or slight inner cone concept. The type of coneconcept refers to the shape of the connector on the apparatus side. Inall three figures an apparatus or accessory 1, 2 and 3 respectively, areindicated to the left. Connectors 4, 5 and 6 are respectively providedwith an inner cone 7, an outer cone 8 and a slight inner cone 9. Theinterface could also be obtained by using plane contacting surfaces.

To the right in FIGS. 1 to 3 are illustrated three cables 10, 11 and 12,respectively provided with terminations 13, 14 and 15 having endsurfaces 16, 17 and 18 fitting the corresponding coned surfaces 7, 8 and9. The conductor joints (plug-in, welding, clamping etc) are not part ofthe present invention and will not be described here. We have onlyindicated cable connectors 19, 20 and 21 on the cable terminations 13,14 and 15 respectively.

In the following detailed description of examples of cable connectionswe have chosen to show the outer cone concept, it being understoodhowever, that the same series of interconnections can be obtained withthe inner cone concept and with the slight inner cone (or plane)concept.

A general advantage of the outer cone concept over the inner cone isthat the outer cone separates the cable connection further from theapparatus it is connected to, than does the inner cone. Hence a fault atone side is less likely to affect the other side.

The inner cone concept would have the advantage that a shorter solutioncould be used outside an SF6 cubicle. Problems with the coned surfacesmay arise when components are made by different suppliers. The apparatusconnectors are usually made of epoxy or similar non-compressible, rigidmaterial, whereas the cable terminations usually are made of rubber andsimilar compressible or elastomeric materials. The outer cone conceptwould have the advantage over the inner cone concept that it is easierto expand the rubber material than to compress it.

An advantage of the substantially plane surface interconnection is thatthis simplifies complete alignment of the meeting surfaces withoutrisking glow discharges.

FIGS. 4 and 5 illustrate the components of an SF6 terminal using theouter cone concept and the present invention. As will be seen from thesucceeding drawings, the concept of the cable termination illustrated inFIG. 4 is the generally applicable building block of all applications.

A cable termination 30 shown in the lower part of FIG. 4 is arranged ona cable end 31 provided with a cable connector 32 and a stress reliefcone 33 comprising a voltage deflector 34 as a stress relief device anda connector shield 35 embedded within a body 36 of elastomericinsulation. The body 36 of elastomeric insulation is covered by aconductive screen 39 and is enclosed within an outer rigid casing 38.

The termination 30 fits to an interface device 40 including a rigidinsulating body 41, e.g. made of an epoxy resin, having a conicalinterface surface 42 which fits to the interface surface 37 of theelastomeric body 36 of the termination 30.

When the interface device 40 is used in connection with an SF6 terminal,the rigid insulator 41 is provided with a connector 43 which may have acompact version 44 or an IEC 859 standard (longer) version 45.

In FIG. 5, an SF6 termination of the present invention is illustrated.In addition to the components 30, 40 and 43, the drawing indicates anSF6 casing 46 and a connector 47. The usual hollow insulator used inconventional terminations is replaced by the compact or rigid epoxy body41 around the conductor.

Advantages over conventional terminals are: Compact design, lowermaterial and installation cost, complete independence between gasinsulated switch gear and cable installations, standardization.

In FIGS. 6 and 7, there are illustrated two versions of transformerterminals. FIG. 6 shows an application of the invention with atransformer 50 having an oil-filled box 51 with a bushing 52 to which acable termination 30 and connector 53 are connected. The connector 53corresponds to the parts 40 and 43 in FIG. 4.

In FIG. 7, a transformer 55 is provided with bushing 56 comprising therigid insulating body 41 with the interface surface 42 which isconnected directly to a cable termination 30, having the correspondinginterface surface 37 as indicated in FIG. 4. This transformer terminalversion is useful with the outer cone concept only. This version impliesenhanced safety due to the omission of the oil-filled box with itshighly combustible oil.

In FIGS. 8 and 9, there are shown two versions of out-door terminals. InFIG. 8, the terminal 60 consists of components 30 and 40 combined with aconductor 61 which together with the epoxy insulator 40 is covered bytracking resistant EPDM rubber or silicone rubber sheath 62. This designeliminates the need for an oil- or SF6 -filled insulator, whilemaintaining the mechanical rigidity of the omitted insulator.

In FIG. 9, the out-door terminal 65 includes a surge suppressor device66. This terminal is in principle similar to that described in U.S. Pat.No. 5,206,780 (J Varreng 6). The device 66, which consists of non-linearmaterial such as ZnO or SiC, is separated from the conductor 67 by alayer of insulation material 68. The interconnctions from the non-linearmaterial layer, at the bottom to ground and at the top to the conductor67 are not shown. The device 66 may be a continuous tube or it mayconsist of a number of series connected annular elements. The device 66and insulator 40 are covered with tracking resistant EPDM rubber orsilicone rubber sheath 69 as in FIG. 8.

FIG. 10 illustrates a straight through joint 70. The epoxy component 40is shaped as a symmetrical double cone which forms a center piece of aplug-in joint joining two cable terminations 30. This design may be moreexpensive than a pure elastomeric joint, but it has the advantage offactory testing and quick installation.

FIG. 11 illustrates a transition joint 75 between a dry cable and anoil-filled cable. The epoxy component may be extended to form aninsulator housing 76 on the oil-filled side 77. Advantages are asabove,--lower material and installation cost as well as a compactdesign.

In FIG. 12, there is illustrated a joint 78 between two apparatus 79 and80, e.g. between a transformer and a switching station. Rigid insulators81 and 82 fastened to the apparatus, e.g., as bushing devices, haveconical interface surfaces 83 and 84 corresponding to the interfacesurfaces 85 and 86 of the connection device 87. This device consists ofa connector 88 for electrical conductors, not shown in this Figure, aconnector shield 89, an insulating body 90 made of an elastomericmaterial and covered by a conductive screen 91. This complete device isenclosed within an outer rigid casing 92.

For optimizing the products described in the above detailed descriptionand for making sure their high operating reliability in high or extrahigh voltage installations an essential characteristic is the outersurface configuration of the rigid insulator having the conicalinterface surface. Therefore, FIG. 13 illustrates a rigid insulator 93,corresponding to the insulator 41 in FIG. 4, to be used in the aboveembodiments of this invention. The claimed angle is the angle betweenthe longitudinal axis 94 and the boundary surface 95 of the insulator93. This angle defining the cone of the insulating body should bebetween 15° and 45°.

The above detailed description of embodiments of this invention must betaken as examples only and should not be considered as limitations onthe scope of protection.

What is claimed is:
 1. Device for interconnecting a high voltage cablewith an apparatus or another high voltage cable, which comprises:(a) acable termination having an elastomeric body with a stress relief deviceand a connector shield integrated therein, the elastomeric body having aconical interface surface and an outer conductive screen theelastermeric body and the outer conductive screen being enclosed withinan outer rigid casing; and (b) a rigid insulator having a conicalinterface surface corresponding to and adapted to mate with theinterface surface of the cable termination.
 2. Device according to claim1, wherein the rigid insulator is made of an epoxy resin.
 3. Deviceaccording to claim 1, wherein the rigid insulator is made of apolyurethane.
 4. Device according to claim 1, wherein the interfacesurface of the elastomeric body is an outwardly extending conicalsurface adapted to fit an inwardly extending conical recess of the rigidinsulator forming the conical interface surface thereof.
 5. Deviceaccording to claim 1, wherein the interface surface of the elastomericbody is an inwardly extending recess adapted to fit an outwardlyextending conical surface of the rigid insulator forming the conicalinterface surface thereof.
 6. Device according to claim 1, the conicalinterface surface of the rigid insulator is defined by an angle in arange of from 15° to 45°.
 7. Device according to claim 1, wherein therigid insulator is fitted to an SF6 terminal.
 8. Device according toclaim 1, wherein the rigid insulator is fitted to a transformerterminal.
 9. Device according to claim 1, wherein the rigid insulatorforms a part of an outdoor terminal.
 10. Device according to claim 1,wherein the rigid insulator forms a part of an outdoor terminalincluding a surge suppressor.
 11. Device according to claim 1, whereinthe rigid insulator forms a part of a straight through joint.
 12. Deviceaccording to claim 1, wherein the rigid insulator forms a part of anoil-filled transition joint.
 13. Device for interconnecting high voltageapparatus, which comprises:(a) rigid insulators having conical interfacesurfaces and fastened to each apparatus being interconnected; and (b) anelastomeric body having a connector shield and an outer conductivescreen integrated therewith, the elastomeric body and the outerconductive screen being enclosed within an outer rigid casing, theelastomeric body having conical interface surfaces corresponding to andadapted to mate with the conical interface surfaces of the rigidinsulators.
 14. Device according to claim 13, wherein the rigidinsulator is made of an epoxy resin.
 15. Device according to claim 13,wherein rigid insulator is made of a polyurethane.
 16. A device foraccomplishing electrical interconnection comprising:(a) an elastomericbody and a connector shield integrated therein, the elastomeric bodyhaving a conical interface surface and an outer conductive screen theelastomeric body and the outer conductive screen being enclosed withinan outer rigid casing; and (b) a rigid insulator having a conicalinterface surface corresponding to and adapted to mate with theinterface surface of the elastomeric body.